This invention relates to the fabrication of a magnetoresistance sensor structure and, more particularly, to one in which the spacer layer is deposited and oxidized in multiple steps for improved magnetic performance.
A magnetoresistance (MR) sensor is used in a read/write head to read magnetic fields on a recording medium of a magnetic storage device. An example is the read/write head of a computer hard disk or a magnetic recording tape. The read/write head is positioned closely adjacent to the recording medium, separated from the recording medium by an air bearing which allows the read/write head to fly over the surface of the hard disk. A data bit is written onto an area of the recording medium using the writing portion of the read/write head by locally changing its magnetic state. That magnetic state is later sensed by the MR sensor to read the data bit.
One of the important types of MR sensors is the giant magnetoresistance (GMR) sensor. The general technical basis, construction, and operation of the GMR sensor are described, for example, in U.S. Pat. No. 5,436,778, whose disclosure is incorporated by reference.
The structure of the GMR sensor includes two thin-film stacks separated by an intermediate nonmagnetic film, typically a copper film, serving as a spacer layer. The lower thin-film includes a magnetic pinning structure, and the upper thin-film stack includes a sensing (free) layer that responds to an external magnetic field. A magnetic biasing structure is present, preferably in the form of a contiguous junction positioned laterally adjacent to the two thin-film stacks and the spacer layer.
The available MR sensors are fully operable and are widely used in magnetic read/write heads. However, there is an ongoing desire and a need to improve their reading performance. The present invention fulfills this need, and further provides related advantages.
The present invention provides a method of fabricating a magnetoresistance sensor structure in which the electrical resistance performance of the spacer layer is improved. Consequently, the performance of the magnetoresistance sensor structure is also improved. The present approach may be practiced using the same fabrication apparatus as in conventional processing, and with only a change to the procedures.
In accordance with the invention, a method for fabricating a magnetoresistance sensor structure comprises the steps of providing a substrate structure (such as an aluminum oxide substrate with a seed structure on it), depositing a magnetic pinning structure on the substrate structure, and depositing an oxidized metallic spacer layer overlying the magnetic pinning structure. The oxidized metallic spacer layer is deposited by the steps of depositing a first metallic sublayer, oxidizing the first metallic sublayer, depositing a second metallic sublayer, and oxidizing the second metallic sublayer. Additional sublayers may be deposited and oxidized as well, in this same alternating deposition/oxidation manner. A sensing structure is deposited overlying the oxidized metallic spacer layer.
The oxidized metallic spacer layer is preferably an oxidized copper spacer layer, and the sublayers are oxidized copper sublayers. A total thickness of the oxidized metallic spacer layer is preferably from about 15 Angstroms to about 25 Angstroms. It is also preferred that each of the metallic sublayer/oxidized metallic sublayer pairs be of about the same thickness.
The deposition of the metallic spacer layer is preferably accomplished by depositing the first metallic sublayer in a vacuum having a first-deposition oxygen partial pressure, oxidizing the first metallic sublayer in a vacuum having a first-oxidation oxygen partial pressure greater than the first-deposition oxygen partial pressure, depositing the second metallic sublayer in a vacuum having a second-deposition oxygen partial pressure, and oxidizing the second metallic sublayer in a vacuum having a second-oxidation oxygen partial pressure greater than the second-deposition oxygen partial pressure. That is, there is usually a small oxygen partial pressure in the vacuum chamber when the metallic sublayers are deposited, and the oxygen partial pressure is increased for the oxidation steps. The oxidation oxygen partial pressure during the oxidation steps is typically of from about 1xc3x9710xe2x88x926 to about 1xc3x9710xe2x88x924 Torr, most preferably about 2xc3x9710xe2x88x925 Torr. The oxygen partial pressure is then reduced for subsequent sublayer deposition steps, if any.
After the sensing structure is deposited, a cap layer is deposited overlying the sensing structure. A magnetic biasing structure is also deposited, preferably in the form of a contiguous junction that laterally abuts the previously deposited magnetic pinning structure and metallic spacer layer on each side. Alternatively, an in-stack magnetic biasing structure may be used. The present approach thus may be used to fabricate a giant magnetoresistance (GMR) sensor.